The Supercharged Audi 3.0T's Fatal Flaw: Why you need to get rid of your OEM Catalytic Converters

In this episode we are going to discuss the one thing EVERY person will have to deal with when owning a car with the Audi 3.0T supercharged engine. This is the Achilles Heel of this engine, and can result in catastrophic failure of your engine when it fails if you don't catch it in time.

[@brittoningraham6056]

In regard to 0:56 I know exactly why Audi choose to place the converters where they are. Basic engineering says the faster a catalytic converter can heat up the more quickly the car will produce clean air out of the tailpipe. The goal is to get the vehicle into closed loop operating as quickly as possible for emissions reasons as well as for wear reasons because when the car runs in open loop you are wasting fuel and diluting engine oil. Faster warm up times are one of the many factors that contribute to the fact we can now get away with changing our oil at 10k + intervals. Also, a hot converter will clean itself better which is probably why these engines can eat 1qt of oil every 600 miles and still not set off a catalyst efficiency codes which has always shocked me since oil does contaminate converters (it says so on your oil filler cap). Oil consumption is probably a huge part of the failure of the original part.

[@Yvqi72]

That would be the PcV being the original failing part.

[@tedjohnson64]

How would faster warmup make longer oil change intervals possible? I’m missing the logical connection there…?

[@brittoningraham6056]

@tedjohnson64 When running in an open loop, the mixture is rich, and excess fuel dilutes the lubrication abilities of the oil while adding contaminants. Closed loop operation is cleaner and more efficient.

[@amedaius8492]

Also the quattro system puts alot of restrictions on the under-the-car space, and people want to keep their cars lowered the most they can for performance and look. The decision simply makes sense.

[@FloridaBikeSupplyOnline]

I was going to say, if you anything the cat is heating the engine. Not the engine heating the cat. The cat burns @ crazy temps, engine is like 200?

[@WhiteTrashPardy]

Where’s a cat thief when u need em

[@fatboyquin]

Knowledge of how to maintain these cars is key and I feel like you’re gonna save so many cars with this series Cam

[@AudiC7Owners]

Much appreciated bro 🙌🏻🙌🏻🙌🏻

[@mab4870]

It was the tune

[@franciscocornejo9753]

@@AudiC7Owners hello how about the 2020 audi a6 3.0t any info on this ones?

[@AudiC7Owners]

That's a C8 with a completely different engine. Not my area of expertise unfortunately

[@prabeeshsidhu]

please never delete these videos!! this knowledge is priceless. Thank you for sharing

[@jonathangipaya]

Such an underrated channel! Appreciate the videos!

[@AudiC7Owners]

Thank you! 🙏🏻

[@lewisthompson8705]

As a new owner to an A6 exactly like yours, these videos are super helpful. Thank you so much! Definitely subscribing

[@AudiC7Owners]

Thanks man! Enjoy the car!

[@cm.5023]

My B6 VR6 Passat had a similar exhaust system but with 4 cats. Thankfully they lasted well over 300k till the trans started slipping. Thanks for your vids, I really enjoy your C7 content.

[@AudiC7Owners]

Thank you!

[@miguelnavarro2571]

Another great video, very informative! Question - How's about a recommendation or video on what you recommend should be the first upgrades or maintenance items on the C7. Surely you have a list of things needing to be addressed right off the bat. Cheers to more great content!

[@AudiC7Owners]

That's a great idea! I'll probably do one of those for you guys soon. But in the meantime you can check out our new owners guide video to learn about pretty much all maintenance issues.

[@lolley1100]

Great write up on it! I had worked at an Audi dealer for several years up until 2021. While I had replaced several sets of cats for catalytic inefficiency faults and cracked flange welds, I had never seen them be the cause of any drivability concerns. After 2021, I had went to an Indy euro shop where I still currently work. It wasn’t until I started actually modifying em where I’ve seen em start to have issues. So far, I’ve only seen 3.0 cats be the cause of an engine failure, which was on an APR stage 3 build. For what it’s worth, I live in one of the hottest and humid climates in the states. In my opinion and experience with these, if it’s modded, ditch em. If not, don’t sweat it! 😁😁

[@Inimbrium]

Dude, this has been happening to my car for years!!! Finally, someone who knows what the problem is!!! Thank you!!!!!!!!! It's a 2012 :)

[@AudiC7Owners]

Get it fixed asap! A scan should tell you if you have catalyst codes as well

[@DeanAndryeyev]

Thanks for this video. Although I'm looking at a B8.5 it was very helpful regarding the motor.

[@dioneyloyola]

This is very true. I had melted pistons all in bank 2 of the engine #6 piston was the worst. My catalytic converter was clogged and it caused my combustion chamber to reach really high temperatures. I did not experience any misfires or rattles until after the damage was done. My data log showed that my cars was running perfectly fine during racing. I learned the hard way

[@AudiC7Owners]

Damn! Sorry to hear that

[@alexburr36]

That’s wild to me! No signs at all?

[@snakkedr]

I'm in the same boat as you are. Spun a rod and had severe knock. Cylinder walls on bank 1 were scored. No misfires prior. My A6 has been stage 2 dual pulley since 2016. I have a slightly lower mileage engine going in with catless test pipes.

[@dioneyloyola]

@@snakkedr mine developed a knock about 5 minutes after I was done racing and in about another 5 it completely siezed. I bought a used engine too but I just gutted the cats. My car is stage 2 double pulley on a e40 tune

[@JoeyS5]

@@dioneyloyola do u know roughly how many miles the car was stock power, stage 1, stage 2 power?

[@davidsibble7429]

Great advise, actually one I’ve thought of often and was more on the side of gutting the cats on my stick system. Good thing is that my car sits at home in the days and I drive a work van, so it’s out sporadically on weekends more than anything else, ( only mods are APR 1 & K&N)

[@AudiC7Owners]

Thanks!

[@Machtig-1]

great info. thinking about moding my A7 and hadn't thought about the cat. great heads up. thank you so much for the vid.

[@AudiC7Owners]

No problem. Good luck!

[@Infantryman662]

Great video! I've heard some people say if you go stage 1 you don't need to do anything to your catalytic converters and like what you're saying if you just boot it a lot (send it) you're at risk. I bought my S4 because of how much fun it is to send it so I'm always booting it. I appreciate you explaining everything in great detail. I am not in an area where I need to pass emissions, but I don't want my exhaust to be louder either. But higher on my list is cost I don't want to spend good money on something that'll fail again down the road. Sounds like I'm going gutted cats, the wife is going to love it haha.

[@AudiC7Owners]

You could buy CAP test pipes & then sell your oem cats to recoup the costs or pay for the labor to remove them.

[@davidallen9246]

This is a great video. Unfortunately, I watched it too late and fell victim to this resulting in catastrophic failure and a blown engine. I bought a 2012 A6 3.0T and went APR Stage 2 with tune and dual pulleys. It was great fun for a few years until it started running rough with misfires. My Indy shop also must not have seen your video and kept replacing coils etc. Then came cylinder 6 catastrophic failure due to exhaust manifold bits going into cylinder I'm guessing. Went the route of putting in a used engine and I pretty much baby the car at this point. Need to show my mechanic this video and address the cat issue before the same thing happens all over again. Thank you for your insight and great video!

[@AudiC7Owners]

That's a painful lesson!

[@mozime2420]

I think this is what I'm going through right now just sent the car in yesterday on a 2012 stg1 , vcdc said piston6 misfire

[@lauretiu]

i did say this before on one of your videos (i live up north too ND, and we get a lot of salt calcium chloride on the road in the winter) there is an easy way to take them out: take your firewall off (takes about 1 hour if you unplug the engine wire harness from the fuse/relay box) that compartmentalizes your engine bay from the washer fluid and brake fluid reservoir and you have so much space to take them out , you won't believe. i took my cats out 3 times out that way and it took me 2.5h to take both of them off( granted i was lucky and i didn't strip the 3 copper nuts at the top) last time i took them off i upgraded to the cenex exhaust that you had in one of your videos

[@davidsibble7429]

What da…?!! Woow Is that really possible?

[@AudiC7Owners]

One day im going to remove the firewall just to test your theory haha. I know how to remove the firewall from a 4.0TT since that is how you change those downpipes as well. I imagine it can't be that different. When you do it, do you pull the cats out of the top?

[@haditaleb4066]

Interesting.

[@antoniodavino5344]

How do you go about starting to take the firewall off. Looking to do this job soon

[@lauretiu]

@@antoniodavino5344 if you can give me a 1 time use email I can send you some pictures from the time I took out the whole engine with the whole front end of the car

[@31marek13]

Hello, very helpful video, i wish i knew this things before. I have A6 C7 with 2.8FSI engine(very similiar to 3.0TFSI but without superchager). Last week when I accelerated uphill, catalyst literally disconect from exhaust manifold. We had to put whole engine from car because there was no place to repair it on car. When we looked on catalyst, it was disconnected from pipe. There wasnt any welds! We had to weld it and other side too for sure. I dont understand why Audi didnt weld it. Decat does not come to mind because of emmision tests every 2 years in our state. I am glad we could repair it and i am glad also that cats were okay because 1cat costs around 2400€. Total price was 1300€ for the repair (because of engine pulling out) but it is still better than buy new ones.

[@AudiC7Owners]

I'm sorry that happened to you!

[@machko1]

Did the exhaust sound raspy with more rattles from the dash area?

[@riyazes]

Great video! Very well explained

[@AudiC7Owners]

Thank you!

[@Da86suvivr]

Incredible video. I was able to get in on the test pipe GB thanks. Im in NY and plan on getting generic cats and install them on my non-reson downpipes to hopefully pass NY OBD emissions and kill the rasp. Hopefully with test pipes and generic cats along with the MF x-pipe and resonator I can accomplish both my goals.

[@jasonh.2731]

Were you able to pass NY emissions and kill rasp with the setup?

[@knightriderfan1]

My B8.5 SQ5 is still on stock cats after 100k miles on Stage 2+ tune. I hope they don't fail on me any time soon cause I'd hate to go through the trouble on getting them replaced! I remember when I went to Stage 2+ a lot of people told me to remove the cats since I lived in a high heat climate but I've had no issue with them so far. Thanks for the tip on the aftermarket test pipes with cats! If mine end up failing I'd probably just replace them with OEM ones.

[@AudiC7Owners]

Just keep an eye on them! Some occasionally a car will last a long time on them. Sounds like you are getting lucky!

[@SC-gm3ry]

I've had my S4 for almost 3 years now (2014) and was told by my shop when I bought it that the slight rattle I was hearing on startup was some of the honeycomb that had broken off of my passenger side cat and was rattling inside. So far it seems to be fine, and I haven't thrown any codes as a result, but it has always bothered me and been in the back of my mind that it could give out. I am running an APR stage 1 tune, and have been considering going single or dual pulley, but I would probably also need to do something about the cats at that time as well. What I had been considering were the Magnaflow high-flow cats, but I was viewing that as a 'permanent' solution and wasn't aware that those would inevitably fail as well. I guess I need to look into the local laws about emissions standards and if I can get away with test pipes... thanks for this useful info!

[@jessecooper537]

The rattle noise, might be your flex pipe rattling, due to bad motor mounts. Which is a common problem with the 3.0 tfsi

[@stevenbeatty2643]

I would bet on the timing chain guide.

[@Lizard6376]

2012 A7, OEM Cats, 155k miles, stage 2 DP since 110k. Fearing the day this happens!

[@AudiC7Owners]

I'd swap Em before you have an issue

[@austinmerrival927]

@Lizard6367 Still running ok, no issues with OEM cats yet? 😅

[@Lizard6376]

@@austinmerrival927 Almost 180k and still no issues. Everyday the anxiety worsens lol

[@austinmerrival927]

@@Lizard6376 🤣🤣 I hope I’m as lucky as you once I go IE stage 2 dual pulley (currently at 91k miles) keeping fingers crossed for both of us lol 🤞🏽

[@jasonh.2731]

@@austinmerrival927 any update on the health of your cats?

[@gratefultedd969]

Excellent information! Thank you.

[@AudiC7Owners]

No problem!

[@ronkirkham3410]

All your videos are 100%.. thanks again

[@carsandstuff711]

Awesome video...thanks for the loads of info

[@AudiC7Owners]

For sure!

[@hondarr9208]

I have 2011 S5 and had this issue. Passengers side cat was busted.. Audi charged me +4000€ to replace a new one.. only the cat cost over 2000€. Not a cheap car to repair. I hope that drivers side cat won't fail on me soon too :D Thanks for great video! I hope I watched this earlier.

[@mariocicciarello2154]

Excellent video and info as usual Cam! Question, do additives like Cataclean every quarter help at all?

[@AudiC7Owners]

Marginally at best

[@mariocicciarello2154]

@@AudiC7Owners I appreciate the quick reply Cam! Have a great week and glad I found you and your expertise!

[@AudiC7Owners]

@@mariocicciarello2154 No problem man! Thank you!

[@bwopyo5703]

Thank you I been dreaming of having a 3.0 tfsi engine

[@RickyPolarz]

Thank you for the info!

[@ronkirkham3410]

Luckily I don't have emissions to worry about and I did would you did on one of my vehicles cut the cats out gutted them and had them welded back in and everything was great. I'm thinking like you said that's the way to go besides removing some resonators and changing the factory mufflers but I don't really want a ton of drone in the car so any input is greatly appreciated

[@planetfade2522]

Very informative video! My car has a vibration at idle but gone with I get to speed.. another thing I wanted to note is that when I start to slown down and at around 2-1200rmps it get worse could it be the cats being clogged ? Thanks and keep up the good worrk!

[@AudiC7Owners]

That's likely not from cats clogging. That could be from engine mounts or control arms wearing out. Do you have any suspension modifications?

[@jacksonfawbush5439]

Thank you for the info.

[@hektorroosileht]

My A7 3.0T has gutted cats but since here in EU it doesnt pass the emissions the last owner had to put universal cats on it(a little bit further away from the engine). It has "custom" exhaust also with deleted o2 sensors(also deleted in the map so no check engine light). The thing is I changed the universal cats(they were like the cheapest ones) with euro5 universal cats but I've been told that those wont last very long either. What would the best plan be, should I get some more expensive sport cats there? What would be the best choice out there that is not very expensive and is available in EU also.

[@nick-qv2iz]

Hey, love your videos! You have a great channel! Question, I have a 2012 Q7 with the 3.0t and I’d like to stage one jackal tune it and maybe stage two down the road…on the q7 as well do you recommend gutted cats? And do you have any heat exchanger recommendations for the q7?

[@AudiC7Owners]

Always mercracing for heat exchangers. And cats are always a concern. I'd have money set aside to deal with them when the time comes.

[@Moments-in-Frames]

Great video, I'm glad i found your channel! I just upgraded from my 2009 a4 to a 2014 a6 3.0T, i love it and I'm trying to take care of it for as long as possible but I'm still learning a lot about the car. At 9:08 you mention the 3 ways you can mitigate the failure of the catalytic converter. My question is, which of the 3 ways is the best and also which is the most cost effective to have done at a local shop? Do you also know the average price I would spend on each? I also looked into the test pipes on can auto and it says that they increase performance but earlier in this video you mentioned that increased performance can quickly wear on the catalytic converters, does that apply with this as well? Thanks in advance, love your videos!

[@AudiC7Owners]

Test pipes = No Cats anymore. It's just a piece of pipe. You will have to call around to find a shop to install them. Will probably be about 6 hours worth of work.

[@Moments-in-Frames]

@@AudiC7Owners thank you! I also notice on the website they have options for a heat shield or black ceramic coating on the pipes. Do you think either of those options are worth it?

[@AudiC7Owners]

I would do the heat shield if it were me

[@Moments-in-Frames]

@@AudiC7Owners thanks a ton!

[@luislooey9727]

​@@AudiC7Owners if we take this route are we looking to change the sound of the exhaust? I don't want to change any sound to be honest

[@chriseastburn3551]

Good info!

[@ronkirkham3410]

Great video man I'm new or new words Audi but not new to automotive in general I've had lots of vehicles 600-horsepower mustangs and GMC big block trucks etcetera but I'm getting a 30 ts5 and I definitely have some questions about the exhaust and would be great if we get touch base even for a couple minutes

[@justfasthd24]

Thank you very much for this video!

[@AudiC7Owners]

💯💯

[@craigauty6756]

Mine are drilled out cats. And done a muffler delete. Sounds better than a friends with a stainless steel full exhaust system. Heard mild steel sounds better than stainless also

[@campbellsoup4910]

Very good information on Cat's. My question is, when you start upgrading power with tuning and pulley's is it a good practice to gut cat's or upgrade exhaust system first? Also, is there a diy way to check condition of Cat's? 2012 A6 prestige sports 3.0t 80k

[@AudiC7Owners]

It's always better to deal with your cats first. An aftermarket exhaust has no performance benefits. Just makes you smile bc of loud noises haha.

[@campbellsoup4910]

@@AudiC7Owners Copy that! Thanks 👍🏾

[@HappyPel]

The reason for them being so close to the engine is for emission efficiency. The faster the cats get hot, the faster they work. This is also the reason for a secondary air injector pump and the grumbly / rich start up on VAG cars. They are all added to make the CATs get hot faster.

[@AudiC7Owners]

That makes sense

[@HappyPel]

@@AudiC7Owners That being said... I have a b8.5 s4 with the same engine / cats. They are absolutely nuts for how they have the passenger side one in. It requires SO SO much work to remove / install.

[@murraydmark]

Does driving with a Check Engine Light from having test pipes hurt anything? Perhaps messing with Air/Fuel mixture? Which would you recommend as far as safety? Not trying to switch tuners right now, and my tuner does not have a test pipe file. Bonus question: the SAI system. If I have test pipes, are the SAI ports less likely to clog? And if they do, would it even matter in my case?

[@AudiC7Owners]

No. A test pipe cel won't hurt anything. Reference the SAI, I'm not sure what makes them clog faster. Not a lot of info out there about it for our engines.

[@LPKizzle]

Commenting on adding a downstream CAT, wouldn't you just get a CEL from the O2 sensor or if you add it downstream you would also need to add the spacers?

[@mastalee1776]

Sucks to be in cali like me. Soo many unnecessary restrictions

[@MyXXXcarlosXXX]

Great video!

[@AudiC7Owners]

Thank you!

[@audikingzz_4053]

I unfortunately had the same problem, which converter do you recommend can you give a link. thanks in advance

[@mtnbikerva1]

93,400 miles stock 2014 Audi Q5 3.0t mostly highway mile, any of this apply to my vehicle? Preventative service beyond manufacture recommendation? If I go stage 1 does it change maintenance and repairs? Thank you!

[@riteshnowbut1898]

Hi Sir very informative video... Tell me someting.. I have a 2011 A6 2.0tfsi... Should i gut out my cat before it clogs? Or do I have to tune the ECU inorder to do so? Also would the car have any performance problems by gutting out the cat converter...?

[@AudiC7Owners]

Your car doesn't have any issues with cat failure so you don't need to mess with it unless you want to for sound purposes.

[@cwmedia_cn]

I wanted to do test pipe for so long but the fact it’s a pain in the butt job scared me away. Then the cat on bank 1 on my SQ5 finally went. Luckily the weld failed and broke off the flange before it did a lot more damage to the engine.

[@jacobstarling4927]

Just hit 67k miles on my stock s5. In California so emissions are a pain, if I don’t plan on going w/ performance mods and don’t abuse it could I see the cats lasting a while longer? great video as always 👍🏼

[@AudiC7Owners]

If your car stays on stock tuning and you don't beat on it very much then your OEM catalytic converters should last a very long time

[@janbochnig3198]

Good Evening, I have a 2017 a7 c7.5 competition stage 2 ( intake, x-pipes ) . So I may get the same issues one day ? I’m planning to get AWE touring Edition exhaust with resonated downpipes. Thank you !

[@boerieza]

When I went Dual Pulley on the SQ5 I had the cats removed completely. Not only did this sound incredibly bad, but the smell from this engine without cats is truly horrible. I opted to install some Magnaflow small-profile cats into my Milltek downpipes, moving it well away from the main source of heat - and that's solved 90% of the problems. It's still a nightmare to tune the exhaust to sound decent on this engine once you've changed/removed the cats.

[@pxrplexed3501]

I have headers jh motorsport high flow catted downpipes and an awe track, if you went with the touring exhaust it would sound much better imo

[@Alcalfa]

It is quite normal to have cats right at the exhaust manifold, my '04 Toyota has them there and the '01 Golf also. Really nothing to be surprised about... This isn't the late 80s any more with them a few feet from the exhaust ports.

[@hyperspaceexplorer5594]

Watching this video makes me close to trading in my 2013 Q5. Currently, there are multiple fault codes-stuck flap open, misfire on cylinder 3, chugging coolant, using too much engine oil

[@AudiC7Owners]

Sounds like you have leaking intercooler cores along with a bad pcv. I definitely would not drive it until you get all of that sorted.

[@user-vo5my2dt2u]

I have a slight rattle at certain RPMs and wonder if it might be leaking some exhaust gases pre/post converter. No codes, misfires etc. Does this seem accurate? Great content as always!!!

[@AudiC7Owners]

That is probably from bad flex pipes, but it would be impossible to tell without an in person inspection

[@user-vo5my2dt2u]

@@AudiC7Owners good point, thank you. I’ll get it to a muffler shop to inspect further.

[@YouTubeHandlesAreStupid]

That was also helpful explaining why the welds need to be reinforced. I didn't think about that... I just knew to do it. Also, JHM relocated cats haven't had a melting issue since they've been pushed to the downpipes. There's been baffle failures due to welds though

[@thomaspagels3511]

They came out with a revised version right? Or are the current versions still having this issue? I've got some JHM test pipes and their catted and baffled downpipes in the mail and after research was under the assumption that the issues have been fixed with poor quality welds. Good to hear that you confirm the JHM cats don't melt now that they are downstream though.

[@YouTubeHandlesAreStupid]

@@thomaspagels3511 Yes supposed to be fixed.

[@jonathanlin4009]

I have an Audi a6 c8 getting a catless dp intercooler Apr intake and a weistec engineering etc and tcu tune next Tuesday so excited

[@grantball5538]

Great video. I’m from the UK and drive a 2011 S5 3.0tfsi. Are there any manufacturers/brands you recommend for test pipes and for the high flow cats to deal with the noise? My understanding is the engine is very raspy if you just fit test pipes on there own. Any help would be massively appreciated as one of my cats is failing. Thanks

[@AudiC7Owners]

I only recommend Can Auto Performance for test pipes. As far as aftermarket cats go, anything hi-flow that you can install downstream will work. Doesn't have to be expensive

[@Rugged_again]

Another great video my guy 👌🏾👌🏾 and I'm glad to hear that the worst part of this motor is just the cats!!!🙏🏾🙏🏾

[@AudiC7Owners]

There are other issues that could happen... It's just with the cats they almost assuredly WILL happen.

[@carlsenx2175]

Great video! Got some misfire on cylinder 1 and 3 couple days ago. Already scheduled a service for carbon cleaning and new fuel injectors but still worrying about cats. Do you have any suggestion for getting a high flow cat? What brand would you recommend or what product? Thank you so much!

[@AudiC7Owners]

Gesi's are the nice ones you can get. Just put them downstream & not in the oem location

[@carlsenx2175]

@@AudiC7Owners Much appreciate you

[@ar00780]

Good video. 👍🏻, I did dual pulley, intake, tune. Lost all compression cylinder one. Wasn't until I yanked the cat, noticed oil pooling out of manifold. Inside of cat cracked. Took head off, broken ring on cyl 1. Wish I saw this video before the mods .

[@AudiC7Owners]

Sorry to hear that man. Tough luck

[@bangurowned]

Sorry to hear man. How many miles were you at? What’s your plan now? Rebuild or swap?

[@ar00780]

@@bangurowned Ya it sucked. It has 137, 000km (in Canada) so 87,000miles. So a baby for my S4. Found a used motor, on a stand now. Replacing pcv, timing chain, carbon clean out, thermostat and any thing ibwont have to worry about. Race pipe and down stream cats. Oh and a clutch too😁

[@bangurowned]

@@ar00780 I’m about to buy a 2016 a6 with 59k miles. So I’m super nervous about this popular problem with them. Would you still buy it again?

[@ar00780]

@@bangurowned I am going to give this 3.0 another chance. This is suppose to be a strong motor. As a mechanic, it makes to much sense that the location of these converters is ridiculous. Watching this video made even more sense. Down stream hi flows. Hope will fix this. In Ontario we still have emissions laws; hence the converters

[@MindOverEverything]

My S4 has 72k miles and has been Stage 1 for about 3k, so I'll need to take care of this sooner than later. I saw a comment down below about removing the firewall(?) to get easier access. Do you know anyone who has done that? Maybe a video or thread somewhere?

[@ciavashshams]

awesome info. Having issues though… had a bad coolant leak that did hydrolock. So new pcv thermostat water pump valve cover gasket intake manifold gasket… Major cleaning and oil flushes. Vehicle runs fine but now i have misfire on 3 and 6. you have two videos that are taking me to different ways. is it the super harder intercooler leak? or is it the clogged cats? I did have cat codes during all this rehab. I really am at a loss at what to do. it’s a 2014 a7 with 91k bought at auction this way. any advice would help! thanks in advance

[@AudiC7Owners]

You can pull the supercharger to look for signs of intercooler core leaks. But if you have cat codes then you need to drive easy until you resolve that

[@martinnikolaev3555]

How did you manage to deal with the O2 sensors after gutting the cats? Is it possible to tweak the ECU, so that it acts as if everything is fine without popping any CELs?

[@09kmacks]

So, I bought a '13 S4 a few months ago, had no issues during the summer, but as soon as it got cold I had a PCV warning about insufficient airflow, solved that by relocating the hose coming from it up by the passenger side quarter panel. and removing that cover over the intake for increased airflow. Since then, no PCV warnings, but I replaced the water pump and had a transmission service done, and now, whenever it's foggy out, or raining, I get a transmission error code/warning that says not to use reverse, and then the TPMS light comes on for a second and then they both go away, but TPMS will keep popping up every other minute until I turn off and restart the car.... please help

[@TheUnhurduv]

Did some research related to gutting the cats and found this potential workaround: The fault code is caused because the exhaust is flowing faster and cooler than the factory downstream O2 sensor is programmed for. Install a spark plug non fouler in the post catalytic converter O2 sensor locations. This will require you to drill the existing hole in the spark plug fouler large enough to accommodate the O2 sensor. Then install the original O2 sensor into the spark plug non fouler. In some cases this will help eliminate the fault code, but this method should only be used for off road applications as it will not meet federal emissions requirements. I saw this in a MT article related to high flow cats throwing codes in the d/s O2. There are also a couple vids for diy.

[@brittoningraham6056]

Oxygen sensors do not sense temperature they sense the amount of oxygen left in the exhaust after combustion. The way fuel is injected creates a wave (very small) of oxygen rich and then oxygen lean air that the front sensors detect that wave then the exhaust gases hit the converters and almost all of the left-over oxygen is used in the chemical conversion process that happens inside the converter creating an extremely flat oxygen lean mixture post converter. This almost waveless signal is highly calibrated, and the aftermarket cats are not matching most likely producing too much of a wave in the signal because they do not convert the exhaust gasses as well.

[@TheUnhurduv]

@@brittoningraham6056 Replace "programmed" with designed in my previous comment. As I understand it, the sensor will not function at all until minimum temperatures are reached (at least 600°F). In which case, a spark plug non fouler would act to retain more heat, while at the same time allowing less exhaust gases to be sampled because of the smaller inlet thereby keeping a fuel rich exhaust from increasing the voltage enough to register as such. This gives a false reading and a voltage that represents an air-fuel ratio close to stoichiometric.

[@brittoningraham6056]

The oxygen sensor heater will take care of the temperature requirement but moving the sensor out of the stream is definitely what makes the wave pattern smaller allowing the car to pass its own emissions inspection.

[@robinmarshall6926]

Thank you once again you are awesome

[@AudiC7Owners]

Happy to help!

[@forgottenknowledge8917]

At 300,000km my cat has done its job. I gutted it two weeks ago and have kept the resonator off. The muffler came of ages ago. All you need is a 45⁰ bend pipe, a metre of straight pipe to have the tip come out before the rear wheel, and some clamps. Band clamps are easy for joining pipes. My little van sounds like an old truck with the loud turbo whistle, haha

[@Mazzerants]

Since pushing the SQ5 after dealing with my cats I keep breaking welds on my exhaust and red Loctite bolts on clamps keep backing out. Crackles and ignition cut are violent. I am going in to get a fab shop to just dump the exhaust under the car. I actually really like the sound with just test pipes. Its throaty and tricks people. Very concussive at idle. You actually feel the pulses. Zero rasp, which reinforces the theory that the exhaust itself makes rasp.

[@AudiC7Owners]

Keep in mind that a supercharged engine needs some backpressure provided by the exhaust.

[@Mazzerants]

​@@AudiC7Owners Engines do not need backpressure. Its bad for the motor, hence why people see a gain when restrictive cats are removed. What a motor needs and people commonly get confused about is exhaust velocity and scavenging. Turbo cars don't have to worry because the turbine wheel has inherent restriction and cant equal out flow unless its twin turbo with a xpipe. But I digress. Pipe diameter, H pipes, and X pipes all play a role in how a motor can expel gases and scavenge flow. Now I might loose out on the bottom end but the nature of the SC 3.0T has it live in the higher range. Think of it like water coming out of a hose and your finger to regulate the pressure. Water pressure is increased and that allows it to move farther with more force but flow in hindered typically and that causes backpressure in this case. More water flows out of the hose with no finger but it docent have velocity. Why the tone of my motor changed from the rasp fest, snappy pops to the deep, concussive burble it is with dumping after the test pipes.

[@garethwood4316]

@@AudiC7Owners Can u back this up with anything. From what I’ve seen over the last few years is that “your engine requires back pressure” is a myth and will never help in gains….

[@AudiC7Owners]

Ultimately what you want in your exhaust is a proper amount of scavenging which basically creates a suction effect that pulls exhaust gasses out which is what the above poster was discussing.

[@alejandrohinojosa7407]

So does this also happen to 23 Q7 models with the 3.0 engine?

[@lestatelvampir69]

Nice video! I was about to buy a B9 S5 Sportback and now I don't know if I need to change my mind....How much do you think installing the cat. converters in the middle of the pipe lines would be? I'm interested as it would be a necessary solution (I don't like to drive slow XD)

[@AudiC7Owners]

This video is about b8/C7 cars. Not b9's

[@lestatelvampir69]

@@AudiC7Owners I see 😅. Do you mean that B9 doesn't have this issue? Thanks for your answer 😊

[@AudiC7Owners]

Not to my Knowledge

[@reelrocknrolla4251]

Does this apply to the newer q7s as well? I think they updated it in 2017

[@dylandalka8700]

Mine did the same thing you were saying about a month ago changed the plugs and coils and it has been fine but now after hearing it makes sense. I only had a misfire in cylinder 1 and 3. However I’m in the military and idk where I could get stationed so I’m scared of failing emissions tests. What would you recommend?

[@AudiC7Owners]

Doesn't your car stay registered in your "home state" while you are in the military?

[@tomnichol8146]

I have a 2012 w/APR Stage 1 with about 76k on it. I don’t beat it but I don’t baby it. If I gut the cats won’t the lack of back pressure cause a problem? Are there O2 sensors I need to retain? If I eliminate O2 sensors won’t it effect the performance of the car? How exactly does one gut a cat? I have no emissions inspections where I live. I was considering the Magnaflow system, would that be annoying with the gutted cats and therefore I should stick with the stock exhaust? I plan to try and head this off before it happens, hence all questions. Thanks for an outstanding video!

[@AudiC7Owners]

1) it won't effect the backpressure enough to effect performance 2)your 02 sensors stay in place, but you will get a CEL. It won't effect performance negatively. 3) remove your cats, then use something to remove the inside material. 4) annoying is subjective to the person. There will be rasp if you don't make sure the aftermarket exhaust is properly resonated.

[@tomnichol8146]

Awesome thank you so much for the quick response

[@ProdByDame]

The test pipe route tends to make the car sound raspier and less refined. Yet I can't find any high flow catalytic converters for this platform. Do you know if there are any cats to replace the OEM ones without going the noisy test pipe route? Or are there test pipes that don't make the exhaust tone so obnoxious

[@AudiC7Owners]

No matter what cats you use, if you put them in the oem location they will fail. If you want cats, relocate them further downstream.

[@abahsain]

i hear the rattle type noise kind of sounds like a garden sprinkler during acceleration. I cant reproduce the sound if the car is standing still and just rev it. nor is the sound present while cruising. i just hear it when accelerating and near a wall or parked cars usually make the sound more audible.. what you think would be the problem.. is it a gasket failure between turbo and catalytic converters??

[@brandonk73]

did you find out where the sound is coming from. I'm having the same sounds rattle after I went stage 2

[@carlwheezer2258]

Hey I need some help! I’ve been saving up for a s4 3.0t for a while now and not one time have I thought about searching up for the common problems until now. I live in California so tampering with the catalytic converter is already a problem so what would you suggest for me to do that could prevent them from failing and that would still allow me to pass emissions over here? Thank you if you can help out!

[@AudiC7Owners]

The only surefire way is to just replace them oem cats or red star high flow cats that allow you to pass emissions. Otherwise you have to try & use 02 spacers with test pipes. Or move out of CA. That would be my first choice.

[@chrisnipple3469]

I really am torn, I am graduating from college in may of 2024 and I just don't know whether to go balls to the wall with my 09 Volvo C30 or trade the poor car in for one of these. I love my C30 and honestly think It could be super cool if I dumped a bunch of money into once I finally get a big boy job.

[@jideodeyemi2502]

Great video, but I have a question about my 2013 Audi A6 C7 3.0t. Everytime I start the car first time in the morning I get a faint smell of engine oil. Is this normal?, because it only happens in the morning and there is no oil leaks anywhere in the engine. My guess was perhaps there is a valve that vents the pressure in the engine every morning. Any ideas?.

[@AudiC7Owners]

Nope. If you smell oil is because it is leaking or burning off somewhere

[@lonniesanchez2732]

Leaky valve cover gasket probably.

[@S60Rguy]

Not sure if you monitor older videos but I wanted to ask what you suggest for my situation (thinking maybe more options available now). 2012 A6 3.0T with dual pulley APR tune. 128k miles and stock cats/exhaust. I've been using my P3 guage to reset the P0420 code for awhile now. At this point the code comes back on the same day I reset it. I also know its probably only a matter of time before P0430 shows up next. Are there any new options for high flow cats since you made this video? I started looking at JHM but i want to keep the car either quiet or tastefully sporty sounding. I also have to be able to pass emissions.

[@AudiC7Owners]

If you are dead set on putting cats in the oem location check out Garage Auto Sports. People are having good luck with them. Otherwise, get test pipes from Canadian Auto Performance and install cats down steam. CAP has catted mid pipes too

[@S60Rguy]

@@AudiC7Owners Thank you!

[@swift__]

Great info, never heard of this. ( 2014 Q7 3.0t ) guess this is something I’d need address then. Also do you have a recommendation for oil catch can?

[@swift__]

What cat would you recommend if you swap to test pipes up front and throwing in cats further back?

[@AudiC7Owners]

We will be installing a catch can after we relocate our pcv. There is not an easy way to run a catch can with an oem pcv system on these engines. And I would just start with any cheap hi flow cat you can find. Doesn't need to be fancy

[@swift__]

@@AudiC7Owners ok cool, thanks for the response. And definitely excited to see the upcoming videos 🤜🏻🤛🏻

[@bsheers2003]

great video... deters me from any idea of making a C7 my next DIY car. still driving an older C5 2.7t allroad, with just 175k miles. if you have any experience with this engine, would love to hear your comments and warnings.... thx

[@AudiC7Owners]

Don't let this deter you... Test pipes on 3.0t's area like turbos on 2.7t's. At least the engine doesn't have to come out to replace the test pipes

[@bsheers2003]

@@AudiC7Owners wondering if you 've seen this video about the 3.0, and what your comments would be: [ kzbin.info/www/bejne/pH_bqmavgalleZI ]

[@1990AngeloS]

Great vid ... I'm buying a 2010 S4 manual Tomo with extended motor plan ... Is there anything I can do without voiding my motor plan ?

[@AudiC7Owners]

That completely depends on the terms of your warranty

[@1990AngeloS]

@@AudiC7Owners cheers bro

[@jefflandquist]

Any issues with the B9 3.0T cars? We have a B9 (2019) S5 cab, and also looking in to a B8.5 SQ5 so this vid popped up. Thanks

[@AudiC7Owners]

Related to their cats? I haven't heard of any issues

[@dittottid]

Hi sorry I did not understand when you said "gut your cats, put them back in" what did you mean by this? Thanks!

[@songhengli7367]

Did you get any error code when the car went into limp mode because of the clogged cats? Thanks for the informative video!

[@AudiC7Owners]

Yes. Your epc light will come on and you will get misfires.

[@songhengli7367]

@@AudiC7Owners I've had EPC light and limp mode during highway pull a couple times (Months in between) just like you described. But VCDS shows error code code P06C 00 Internal Control Module Main Processor Performance. I wonder if it's cats related.

[@AudiC7Owners]

Sounds like you need to take it to get diagnosed somewhere.

[@YouTubeHandlesAreStupid]

With everything that's been discussed lately, you could make the same video about the Injectors... 034 is recommending that people look at replacing these when over 50k miles.

[@AudiC7Owners]

Discussion on injectors is a relatively new topic, but I think it's good people are talking about it. I need to educate myself a bit more in them before I do a video.

[@danthemansrepreviews5644]

I'm guessing you have c6 experience? And this goes for the 2010 c6 model as well? Both my flex pipe, Which I just saw from your schematic, I think Come right off the catalytic converters, right? Mine just started leaking. So this is right were you said is impossible to get to, correct? So I might as well have the cats removed/gutted when I replace them?

[@AudiC7Owners]

I actually don't have any hands on existing sub the C6, but the cats should be the same in terms of their placement.

[@ianirving8494]

I have a ‘16 C7.5 with around 65k miles. Totally stock, driven hard on occasion for short periods of time, but pretty casual most of the time. Haven’t noticed any oil consumption issues or misfires. Should I be concerned about this yet?

[@AudiC7Owners]

Generally, stock cars that aren't driven hard shouldn't need to worry about this... But it's something to be aware of

[@guydickes2177]

Interesting comment on the EPC code. Happened to wife. 2017 S5. Went into limp mode. on restart the problem went away. As the car was under warranty (3 years, 10,000 miles) I brought into Audi. After testing, etc. the comment was basically- "drive the car hard(er)". It was used around town too much and needed to open up a lot more. After this advice it runs fine.

[@AudiC7Owners]

That could have been from carbon build up on the valves. I assure you my car has no issues being driven hard daily 😂

[@mephistohate]

Australian 2012 A6 C7 3.0T running IE stage 2 dual pulley, had my exhaust shop install some high flow cats, he was able to remove the stock cats out through the suspension area and installed the high flow cats further along the exhaust, have some O2 sensor extensions and O2 sensor spacers, still gives an engine light now and then but i can live with that

[@AudiC7Owners]

Nice!

[@alexp8913]

How much at risk is a stock a6 to melting? I know that going stage 1 or 2 makes it worse but if I wanted to keep it stock besides maybe intake and exhaust do I need to remove them?

[@AudiC7Owners]

It's at risk, but there will be symptoms. Just pay attention to the car

[@calebshauer2348]

This video gave me some piece of mind, but left me with questions as of what to do next. I had the exact issue you described when you send it just for the epc light to come on. I checked the codes and got one for cat efficiency but just recently checked again and it said I had a misfire on cylinder 3. I’m not sure what to do from here, if I should replace the pcv or change the cats but the guy I bought it from said the cats were gutted. The pcv hadn’t been replaced yet either with the car at 130,000km What should I do from here? Change the pcv pre maturely or ignore it and chalk the issue up to bad cats?

[@AudiC7Owners]

If you are getting cat efficiency codes I'd send a borescope into the 02 sensor port to verify. If they are indeed gutted, then just address the misfire (we have a video on how to do that)

[@calebshauer2348]

@@AudiC7Owners thanks for getting back to me so quickly. The cats are gutted but I also don’t believe it is a misfire. The engine runs very smooth and doesn’t have any symptoms of a misfire. Could it be build up in the cats? Or would it be the pcv if it isnt a misfire

[@AudiC7Owners]

Pcv wont cause misfire codes. If you are getting misfire codes then something is going on. Check your coil packs/spark plugs first

[@danielbanani4463]

I wish i would have foud your video earlier. Nice video helped me out alot thank you

[@ezveedub238]

The cats are mounted close to the exhaust because they have to heat up faster to meet stricter emission requirements. Second, they don't fail often, at least not on the dealer repair side with 3.0T. Older 2.7T and 4.2 V8, they failed at higher mileage more than 3.0T. Modified cars, this may be different.

[@AudiC7Owners]

In the modified world it isn't if they will fail, but when lol. And even my friends who is a tech at a dealer told me they deal with failed cats on 3.0t cars all the time on stock cars 🤷🏻‍♂️

[@ezveedub238]

@@AudiC7Owners I don't know about failures in stock cars being an issue. And that's from several dealers I know. They don't even have those cats in stock either checking inventory.

[@funnyshit54321]

I just replaced my PCV and it was ugly ontop of my valves on cyl 3 where I was getting the misfire. I’ve felt as if I been lucky at 125k and cats not showing symptoms. I wonder if there is a way to gut the cats in the car?

[@AudiC7Owners]

You have to remove them to gut them

[@rushi32400]

this video seems like a sign. my s5 has been burning oil. not too much but every 1000 miles or so not exactly sure it’ll be down half a court. also lately i’ve been stepping on the accelerator and my car would go into limp mode and the epc light would come on. first time it happened my intake cone fell off. second time intake was fine and i started the car and the epc light was off. could this be bad catalytic converters?

[@AudiC7Owners]

That is definitely a common symptom. I'd get it checked out to be safe.

[@rushi32400]

@@AudiC7Owners what would you say is the best replacement for them? oem or maybe something aftermarket?

[@AudiC7Owners]

I'd go with test pipes from Can Auto Performance. We are actually about to do a group buy with them for discounted prices.

[@luisencarnacion251]

What O2 spacers are you using? I have Redstar test pipes with redstar 45⁰ spacers, but CEL comes on sometimes.

[@AudiC7Owners]

I'm not running any. But you should run 180° spacers

[@luisencarnacion251]

@@AudiC7Owners 180⁰ spacers?? Where can I find those. I can only find 45⁰ and 90⁰ and a Vibrant J spacer

[@AudiC7Owners]

Can Auto Performance

[@garys7410]

I have a 2016 c7.5 stock daily driven no tracking or anything, what about the oil i recently took your advice changed oil with motul 0w40 x max 100% synthetic. Its a full SAPS oil people say it can degrade and clog the cats quicker...whats your take on it? Im a fan from 🇨🇦

[@AudiC7Owners]

The only way oil will clog the cats is if your car is burning it excessively like when your pcv fails. As long as you monitor your oil consumption and stay on top of it then you should be good for a long time.

[@garys7410]

@@AudiC7Owners good to know, hit 65000kms no burning or top ups in between oil changes 🤞